A widely used method for implementing a dual speed control for automotive applications using permanent magnet (PM), direct current (DC), brush motors is shown in FIG. 1. The relays K1 and K2 are included in the vehicle electrical system. K1 is used to connect the motor M to the power supply via the serial resistor Rs, for low speed operation. K2 is used to connect the motor directly to the power supply, for high-speed operation. Both relays are fully controlled by the vehicle computer. However, the system of FIG. 1 does not provide stall protection for the motor.
Accordingly, there is a need to provide speed control combined with a stall protection feature, wherein existing relays are employed for both features.